Six-Fold-Realm
The Six-Fold-Realm, which is what human physicists know as Calabi-Yau Space, are the six higher dimensions that are separated from the ordinary five by the Ancient Covenant. In the Six-Fold-Realm, the Council of the Guardians of Time are the Six-Fold-God and all Transcendental Beings live and feed on the energies within the Realm, save for the Chronovores who live in the Time Vortex but may feed in the Realm. Both the Six-Fold-Realm and N-Space are inextricably linked by the Vortex.
Ancient Covenant
The Ancient Covenant governs transcendental beings' behavior, seeming to be the physical laws set down after Event One. The Time Lords are aware of the Covenant, which forbids them from attempting to reach the Six-Fold-Realm. It also forbids the union of Eternals and Chronovores, the former exiling the latter after seeing them as parasites on the Realm. (PDA: The Quantum Archangel)